refactor: replace book details GET route with server action

src/app/actions/books.ts

@@ -0,0 +1,36 @@
+"use server";
+
+import { BookService } from "@/lib/services/book.service";
+import { AppError } from "@/utils/errors";
+import type { KomgaBook } from "@/types/komga";
+
+interface BookDataResult {
+  success: boolean;
+  data?: {
+    book: KomgaBook;
+    pages: number[];
+    nextBook: KomgaBook | null;
+  };
+  message?: string;
+}
+
+export async function getBookData(bookId: string): Promise<BookDataResult> {
+  try {
+    const data = await BookService.getBook(bookId);
+    const nextBook = await BookService.getNextBook(bookId, data.book.seriesId);
+
+    return {
+      success: true,
+      data: {
+        ...data,
+        nextBook,
+      },
+    };
+  } catch (error) {
+    if (error instanceof AppError) {
+      return { success: false, message: error.code };
+    }
+
+    return { success: false, message: "BOOK_DATA_FETCH_ERROR" };
+  }
+}